GM says Chevy Volt electric car gets 230 miles per gallon

DETROIT -- General Motors let loose an eye-popping number on Monday: Its coming Chevy Volt plug-in hybrid car will get 230 miles per gallon.

The number is based on tests GM did using an Environmental Protection Agency draft proposal for calculating "mpg" for electric cars — and leaves many wondering if the Volt can actually achieve such an amazing feat.

The answer is maybe yes, maybe no. And maybe it doesn't matter much anymore.

That's because people increasingly may have to find a new number to compare vehicle fuel efficiency. Since the Volt can go 40 miles per plug-in charge using no gasoline, many drivers may rarely burn a tankful. An onboard gas engine charges the battery to extend its range to 300 miles.

The coming all-electric Leaf from Nissan, which claims the car will get 367 miles per gallon under the same EPA formula, actually has no gas engine or tank on board. Leaf will go about 100 miles per full battery charge.

We'll likely end up talking about "price per mile" — the cost to drive the car a mile — says Reilly Brennan, editor in chief of AOL Autos. GM calculates that at about 3 cents per mile for Volt.

"Eventually, it will change, because we're going to be getting our fuel from many different buckets — electricity, hydrogen, biofuels," Brennan says. "I think it will take about five years before people are talking about this differently."

The EPA has not tested GM's claims and can't confirm the fuel-economy figures, the agency said in an e-mailed statement. Brennan says he hopes GM has learned from its past mistakes and is not overpromising on the fuel economy.

Brett Smith, an alternative technology analyst at the Center for Automotive Research, says GM's next step should be to brace consumers for some disappointment.

On average, he says, vehicles get about 15% to 20% worse fuel economy than the government ratings. That usually doesn't faze consumers when the difference is, say, 20% off 20 mpg. But 20% off 230 mpg, would mean coming up 46 mpg short.